Jurgen Klopp rejected an outlandish attempt to lure him back to Borussia Dortmund in 2018 but the Liverpool boss has admitted he would consider returning in future. 

The German left Signal Iduna Park after seven seasons - during which time he won two Bundesliga titles - shortly before moving to the Premier League in October 2015.

Last season's Champions League triumph cemented his rich reputation at Liverpool but just a year earlier he had been offered a route back to Dortmund.

The audacious effort to persuade Klopp to leave behind his work on Merseyside has come to light in Hans-Joachim Watzke's new book, 'Real Love: A life with BVB'.

Dortmund was searching for a permanent successor to the sacked Peter Bosz in May of last year when chief executive Watzke placed a call to Klopp, who was in the middle of a plane trip.

"At some point my phone rang while I was on the plane and Aki [Watzke] was on it, 'Jurgen, you have to come back'," Klopp said, according to an excerpt published by Sport Bild. "I laughed, I thought he was kidding. 'Are you stupid, have you been drinking? How do you get that idea? I have a few more years in Liverpool'.

"I do not know how serious he was at that moment, but I realised that he wanted me to be more willing to respond."

Watzke conceded he "knew" Klopp would honour his contract at Liverpool but said he felt obligated to pose the question to Dortmund's longest-serving coach.

There could, however, be hope for the future, with the Reds boss not willing to rule out a second stint with his former employers.

"As a rescuer, if the club really needs my help, why should I not do it? It's very nice that I would even have the opportunity," he said.

"But I do not think it's very likely that it will happen."